There is a tremendous and growing need for rapid and accurate analysis of biological and chemical samples, both in a hospital/clinical setting and in a laboratory/research setting. Automated preparation and handling of biological and chemical samples can provide an efficient and cost effective answer to this growing need. Many existing devices have been developed to meet this need. However, the prior art has heretofore been characterized by a number of shortcomings.
Many prior art fluid control devices are characterized by an inverse relationship between the speed with which samples are analyzed and the accuracy of the analysis obtained. Such devices are unable to analyze samples both quickly and accurately, and must sacrifice some performance in one to achieve increased performance in the other. For example some pre-existing apparatus increase the speed with which samples are analyzed by simply running faster and pushing the sample faster through an analytical instrument, such as a particle analyzer, flow cytometer or cell sorter. However, the fluid may be moving through the analyzer at faster than optimal speeds, which may decrease the accuracy of the analysis obtained.
Many prior devices are limited to sampling a fixed volume. These devices typically are capable of analyzing only relatively small samples and are thus not useable for analyzing rare events, which typically require large sample sizes.
Another problem with many prior devices is a cross contamination level between samples (often called carryover) of 5% and more. Cross contamination between samples reduces the accuracy of sample results.
Other pre-existing systems are useable only with pre-prepared samples, and cannot be used to prepare, mix and analyze samples. This can be a disadvantage where samples must be analyzed very quickly after preparation, and may also increase the cost and expense of analyzing a sample, as additional equipment must be obtained to prepare the sample in advance of using the fluid control device.
Some fluid handling systems pressurize sample wells to force samples into the system. This method is not useable with filter-bottom plates. Still other systems are configured so that they inadvertently dilute samples, or are unable to pump an accurate volume or at an optimal and accurate flow rate.
What is needed is a fluid handling system that overcomes some of the disadvantages of the prior art by providing a system that is (1) capable of analyzing more accurately and more quickly than pre-existing devices; (2) capable of preparing samples prior to introducing the samples to an analyzer; (3) having a selectable volume; (4) capable of minimizing sample carryover to approximately less than 0.05%; (5) capable of utilizing the full volume of sample; (6) capable of providing accurate sample per unit volume without severely reducing throughput; (7) capable of cleansing the sample probe, thus reducing carryover and contamination between samples; (8) and having means for preventing the mixing of sample and fluids en route to an analytical instrument. The present invention is designed to meet these needs.